Subject: [spring] I-D Action: draft-previdi-spring-problem-statement-02.txt

From: [email-masked]
Date: Fri, 04 Apr 2014 12:37:39 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
 This draft is a work item of the Source Packet Routing in Networking Working Group of the IETF.

        Title           : SPRING Problem Statement and Requirements
        Authors         : Stefano Previdi
                          Clarence Filsfils
                          Bruno Decraene
                          Stephane Litkowski
                          Martin Horneffer
                          Ruediger Geib
                          Rob Shakir
                          Robert Raszuk
	Filename        : draft-previdi-spring-problem-statement-02.txt
	Pages           : 19
	Date            : 2014-04-04

Abstract:
   The ability for a node to specify a forwarding path, other than the
   normal shortest path, that a particular packet will traverse,
   benefits a number of network functions.  Source-based routing
   mechanisms have previously been specified for network protocols, but
   have not seen widespread adoption.  In this context, the term
   'source' means 'the point at which the explicit route is imposed'.

   This document outlines various use cases, with their requirements,
   that need to be taken into account by the Source Packet Routing in
   Networking (SPRING) architecture for unicast traffic.  Multicast use-
   cases and requirements are out of scope of this document.

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-previdi-spring-problem-statement/

There's also a htmlized version available at:
http://tools.ietf.org/html/draft-previdi-spring-problem-statement-02

A diff from the previous version is available at:
http://www.ietf.org/rfcdiff?url2=draft-previdi-spring-problem-statement-02

Please note that it may take a couple of minutes from the time of submission
until the htmlized version and diff are available at tools.ietf.org.

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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From: "Stefano Previdi (sprevidi)" <[email-masked]>
Date: Fri, 4 Apr 2014 19:39:35 +0000

All,

this is the new version of the problem-statement draft incorporating 
the latest comments.

Thanks.
s.

On Apr 4, 2014, at 9:37 PM, <[email-masked]> wrote:
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---

From: Yakov Rekhter <[email-masked]>
Date: Fri, 4 Apr 2014 13:53:20 -0700

Stefano,

> this is the new version of the problem-statement draft incorporating 

Section 5.1.1.2 is clearly an improvement over what was in the
previous version, although some text is still problematic.
Specifically, "C only installs the path via AS2 in its RIB." If it
is the Adj-RIB-Out, then C wouldn't be able to advertise the path
via AS3 inside AS1 (as this path is not in the Adj-RIB-Out).  And
if it is the Loc-RIB, then the Adj-RIB-Out would have only the path
via AS2 (as the Adj-RIB-Out is populated from the Loc-RIB), and C
would not be able to advertise the path via AS3 inside AS1. Either
way, this would contradict the assumption that "C propagates all
the paths to Z within AS1 (add-path)."

You addressed one part of my comments on section 3. However,
the other part of my comments on section 3 is still not addressed.
Specifically, section 3 of draft-previdi-spring-problem-statement-02 
still contains the following:

   The source-based routing model, applied to the MPLS dataplane, offers
   the ability to tunnel services (VPN, VPLS, VPWS) from an ingress PE
   to an egress PE, with or without the expression of an explicit path
   and without requiring forwarding plane or control plane state in
   intermediate nodes.

The above claim about the ability to tunnel services is misleading,
as VPN and VPLS services may use p2mp or (in the case of VPN) mp2mp
LSPs, and providing any capability for setting up such LSPs is not
in the SPRING charter.

With this in mind I propose to replace the above with the following:

   The source-based routing model, applied to the MPLS dataplane, offers
   the ability to tunnel services (VPN, VPLS, VPWS) from an ingress PE
   to an egress PE, with or without the expression of an explicit path
   and without requiring forwarding plane or control plane state in
   intermediate nodes, but only if such tunnels are neither p2mp
   nor mp2mp tunnels.

Yakov.

---

From: "Stefano Previdi (sprevidi)" <[email-masked]>
Date: Mon, 7 Apr 2014 10:38:36 +0000

Hi Yakov,

> the paths to Z within AS1 (add-path)."

I'll address your BGP concerns on a separate thread.

> You addressed one part of my comments on section 3.

it's already good to hear/read that ;-)

> However,

fine by me, I'll incorporate your comments. Thanks.

s.

---

From: "Stefano Previdi (sprevidi)" <[email-masked]>
Date: Thu, 10 Apr 2014 16:16:20 +0000

Hi Yakov,

see below a comment I forgot to answer...

>> the paths to Z within AS1 (add-path)."

you're right, the statement that is confusing is "C only installs 
the path via AS2 in its RIB".

Anyway, we have re-phrased the whole section and I'm about to submit 
a new version of the draft.

Thanks.
s.

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